Bead ring assembly for vehicle tyres

Abstract: A bead ring arrangement is described for vehicle tyres in which the wire layers (5,6,7) of the wire bundle are wound from a single wire (4) and the wire layer (7) at the core apex side has fewer turns than the wire layer (6) lying beneath it.

Description: The invention relates to a bead ring assembly for vehicle tyres of a ring-like rubberised wire bundle of several wire layers arranged above one another and a bead apex comprising an elastomeric material, arranged adjoining the wire bundle and extending in the direction of the side wall of the tyre. Bead ring assemblies of the kind are generally known for example from FR-A-2374173 corresponding to the preamble of claim 1. In such assemblies the rings which are essentially non-extensible in the radial direction are so wound that several wires which lie alongside one another, and which have been combined by rubber material into a band-like strip, are wound into a ring with several wire layers above one another. As a rule wires are used with a relatively small diameter below 1mm. Despite this small diameter of the wires the start and end of the winding have an unfavourable effect with respect to the uniformity of the tyre, even with corresponding mutual displacement of the beginning and end of the winding. Such bead rings are also known wound so that the ring surface defined by the radially inwardly disposed wire layer extends slightly conically so that an adaptation can be achieved to the shape of the associated surface of the rim seat. In this way a uniform contact pressure is achieved when the tyre is installed on a wheel rim. For bead ring arrangements formed in this way the danger exists that faulty installation of the bead ring takes place during tyre manufacture and that the angle of inclination of the radially inwardly disposed wire layer does not extend in correspondence with the inclination of the associated surface of the bead seat but rather opposite thereto. This faulty installation of the bead ring is practically not recognisable in the finished tyre but can however lead to the tyre provided with the faultily installed bead lifting in certain driving situations from the surface of the rim seat. A sudden pressure loss in the tyre can thereby occur causing critical driving situations. The object of the invention is to design a bead ring arrangement of the initially named kind in such a way that the effects resulting from the bead ring layout on the tyre uniformity can be at least substantially reduced, in particular with a simultaneous reduction of the manufacturing costs, and in such way that the danger of faulty installation of bead rings into the respective tyre is practically precluded by the bead ring layout. This object is satisfied in accordance with the invention essentially in that the wire bundle is wound from a single wire; in that the number of wire turns lying alongside one another is different in at least two of the wire layers arranged on top of one another; in that the number of adjacent wire turns in the wire layer adjacent the bead apex is less by at least two turns than the number in the wire layer lying directly beneath it; and in that the mutually oppositely disposed surfaces of the wire bundle and the bead apex are of complementary shapes such that the bead apex contacts the wires of both wire layers in form-matched manner. More preferably the number of adjacent wires is two turns less than the number in the wire layer lying directly below. Through the winding of the wire bundle from a single wire, in particular from a rubberised single wire, the points of abutment susceptible to breakage which are present in customary bead rings, and which can have an unfavourable effect on the tyre uniformity, are avoided. Moreover, a wire of larger diameter can be used for the winding of the bead ring which leads to a notable reduction of cost and also to a desirable reduction in weight. It is of particular significance that the bead ring winding is executed in such a way that the number of wire turns lying alongside one another in the wire layer adjacent the bead apex is less by at least one turn and preferably by two turns than the number of windings in the wire layer lying directly beneath it, with the bead apex then simultaneously being so executed that it contacts both the accessible layers essentially in a form-fitted manner. This leads to a situation in which, during installation of the bead ring arrangement, not only the layout of the wire layer at the bead apex side provides a criterion for the correct installation of the bead ring in the tyre but rather the previously installed unit of the bead ring and the bead apex which have been put together in the certain manner can only be correctly built into the tyre as a result of the preforming of the bead apex. In this way the initially indicated dangers of faulty installation of a bead ring arrangement with a conically extending inner surface are removed. Particularly advantageous embodiments of the invention are set forth in the subordinate claims. The invention will now be explained in more detail with reference to exemplary embodiments and to the drawing; in the drawing there are shown: Fig.1. a schematic illustration of a bead ring region of a vehicle tyre with a bead ring arrangement formed in accordance with the invention Fig. 2 an illustration correspondence essentially to Fig. 1 in a modified embodiment, Fig. 3 a schematic illustration of a bead region of a pneumatic vehicle tyre with a further variant of a bead ring arrangement in accordance with the invention, and Fig. 4 an illustration corresponding essentially to Fig.3 with a bead ring arrangement modified in comparison thereto. Fig.1 a bead region of a motor vehicle tyre comprises a bead ring formed from a wire bundle 1 with an associated bead apex extending from the bead ring in the direction of the sidewall 3. The bead ring is wound from a single wire 4, in such a way that a lower wire layer 5, a middle wire layer 6 and an upper or bead apex side wire layer 7 is obtained. The wire bundle 1 formed in this way is embedded in the customary manner in rubber compound and forms an essentially non-extensible ring. The lower wire layer 5 consists of four windings or turns lying alongside one another, the middle wire layer 6 consists of five turns or windings lying alongside one another, and the wire layer 7 at the bead apex side consists of two turns or windings with the individual wire 4 being so wound that these two windings are positioned nearer the inside of the tyre in the axial direction. For the winding a single wire is used with a diameter of preferably approximately 1.4 mm whereby it is possible to obtain, on the one hand, a saving of cost and, on the other hand, a saving of weight of 20%. The use of an individual wire of this wire thickness has no negative effects on the tyre uniformity since, as a result of the winding being a single wire, no point of abutment arises which extends over the full width of the bundle, as in customary wire bundles wound from a strip of parallel wires embedded in rubber. Instead only two single wire ends are present which can in turn be displaced relative to one another and are preferably disposed diametrically opposite to one another. As the layout of the wire layer 7 at the bead apex side is in the form of only two windings a non-symmetrical assembly in cross-section results which makes it possible to recognise at once during the installation of the bead ring due to it being visible in the outer side of the bead ring. This is of substantial importance in bead rings which are so wound to match the rim seat surface with a conical ring surface 8. Such beads may have an inner surface which has for example an inclination of 5°. A bead ring formed in this way must be so built into the tyre that this inclination extends in the same direction as the bead toe inclination, since only then is the required uniform contact pressure at the rim ensured. In the event of a faulty installation of the bead ring, i.e. an installation with the contrary inclination of the ring surface 8, extremely dangerous pairings of tyres and rims can result so that it is of substantial importance to fundamentally preclude such faulty installations. When the wire bundle 1 wound in accordance with the invention is combined with the bead apex 2 into a sub assembly the wire bundle pack 1 and the bead apex 2 can only be combined or assembled in the correctly defined manner because of the stepped layout of the wire layer at the bead apex side, since the mutually oppositely disposed surface of the wire bundle 1 and the bead 2 are of complementary shape. As a result of the deformation of the core apex one obtains in this manner an overall unit which precludes any form of faulty installation. Fig. 2 shows a modification with the winding being so executed that the two windings of the layer 7 at the bead apex side are disposed at the axially outer side of the tyre. Through the positioning of these windings at the bead apex side, which leads to a lack of symmetry in the layout of the wire bundle 1, the running behaviour of the tyre can be intentionally influenced. The illustration of Fig. 2 furthermore makes it clear that the principle of the bead core layout is realisable with a different number of turns per wire layer with the fundamental hexagonal structure however being retained. In the variant of Fig. 3 the winding is laid out in such a way that two middle wire layers 6 are formed between the lower wire layer 5, i.e. the radially inwardly disposed wire layer, and the layer 7 at the core apex side which consists solely of one turn. The upper layer 7 consisting solely of a single turn is thereby disposed at the inner side of the tyre and the core apex 2 is again corresponding adapted shapewise and lies on the upper winding 7 and the layer 6 lying beneath it. Fig. 4 shows a variant of the embodiment of Fig. 3 in which the upper wire layer 7 consisting of a single winding or turn is disposed towards the outer side of the tyre and is surrounded at both sides by the bead apex 2. The advantages described above apply for all the illustrated variants.

Claims: A bead ring assembly for vehicle tyres comprising a ring-shaped rubberised wire bundle (1) consisting of several wire layers arranged on top of one another, and a bead apex (2) comprising elastomeric material, arrange adjacent the wire bundle (1) and extending in the direction of the side wall of the tyre (3), the wire bundle (1) being wound from a single wire (4) and the number of wire turns lying alongside each other is different in at least two of the wire layers (5,6,7) which lie on top of one another, the number of wire turns lying alongside each other in the wire layer (7) at the bead apex side being smaller by at least two turns than the number in the wire layer (6) lying directly underneath it; characterised in that the mutually oppositely disposed surfaces of the wire bundle (1) and the bead apex (2) are of complementary shapes such that the bead apex (2) lies on the wires of both wire layers (6,7) in a form matched manner. A bead ring assembly according to claim 1, characterised in that the number of wire turns is smaller by two turns than the number in the wire layer (6) directly underneath it. A bead ring assembly in accordance with claim 1 or 2, characterised in that the diameter of the single wire (4) is larger than 1mm. A bead ring assembly according to claim 1 or 2, characterised in that the diameter of the single wire is in the range of 1 to 1.5mm. A bead ring arrangement in accordance with any or claims 1 to 4, characterised in that the wire bundle (1) is constructed with a substantially hexagonal cross-section. A bead ring assembly in accordance with any one of the preceding claims, characterised in that the wire layer (7) at the side of the bead apex has one wire turn and in that the bead apex (2) extends beyond said wire turn on one side and also is supported by the underlying wire layer (6). A bead ring assembly in accordance with any one of claims 2 to 6, characterised in that the two wire turns of the wire bundle (1) at the bead apex side, lie on the side disposed towards the inner wall of the tyre; and in that the bead apex (2) engages over the two wire turns at one side. A bead ring assembly in accordance with any one of the preceding claims, characterised in that a single wire turn is used for the wire layer (7) on the bead apex side and the bead apex (2) overlaps this wire layer on one side and contacts the underlying wire layer (6). A bead ring assembly according to claim 8, characterised in that the bead apex (1) overlaps both sides of the wire layer (7). A bead ring assembly in accordance with one of the preceding claims, characterised in that the ring are (8) defined by the radially inwardly disposed wire layer (5) tapers down conically in the direction of the inner side of the tyre. A bead ring arrangement in accordance with claim 10, characterised in that the angle of inclination of the ring surface (8) is approximately 5° relative to the associated tyre axis.

Inventors: GLOTZBACH KLAUS-DIETER, GLOTZBACH, KLAUS-DIETER
Applicants: SP REIFENWERKE GMBH
Application year: 1994
Main classification: B60C15
IPC codes: B60C15